Composite spoolable tube

ABSTRACT

A spoolable composite tube capable of being spooled onto a reel for storage and for use in oil field applications. The spoolable tube exhibits unique anistropic characteristics that provide improved burst and collapse pressures, increased tensile strength, compression strength, and load carrying capacity, while still remaining sufficiently bendable to be spooled onto a reel in an open bore configuration. The spoolable composite tube can include an inner liner, an interface layer, fiber composite layers, a pressure barrier layer, and an outer protective layer. The fiber composite layers can have a unique triaxial braid structure.

RELATED APPLICATIONS

The current application is a continuation of U.S. patent applicationSer. No. 10/041,247, filed on Jan. 8, 2002, which is a continuation ofU.S. patent application Ser. No. 09/875,561 filed Jun. 6, 2001, now U.S.Pat. No. 6,357,485; which is a continuation of U.S. patent applicationSer. No. 09/597,201 filed Jun. 20, 2000, now U.S. Pat. No. 6,286,558;which is a continuation of U.S. patent application Ser. No. 09/295,289filed Apr. 20, 1999, now U.S. Pat. No. 6,148,866; which is acontinuation of U.S. patent application Ser. No. 08/804,790, filed Feb.24, 1997, now U.S. Pat. No. 5,921,285; which is a continuation-in-partof U.S. patent application Ser. No. 08/720,029, filed on Sep. 27, 1996,now U.S. Pat. No. 6,016,845 which claims the benefit of U.S. ProvisionalApplication No. 60/004,452, filed Sep. 28, 1995. Each of theaforementioned patents and patent applications is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates generally to spoolable tubing suitable foruse in the oil industry, and more particularly to spoolable tubingconsisting of a composite material with the ability to withstand highstress.

Spoolable tubing, that is tubing capable of being spooled upon a reel,is commonly used in numerous oil well operations. Typical oil welloperations include running wire line cable down hole with well tools,working over wells by delivering various chemicals down hole, andperforming operations on the interior surface of the drill hole.. Thetubes used are required to be spoolable so that the tube can be used inconjunction with one well and then transported on a reel to another welllocation. Steel coiled tubing is typically capable of being spooledbecause the steel used in the product exhibits high ductility (i.e. theability to plastically deform). Unfortunately, the repeated spooling anduse of steel coiled tubing causes fatigue damage that can suddenly causethe steel coiled tubing to fracture and fail. The hazards of operatingsteel coiled tubing, i.e. risk to personnel and high economic costresulting from down time needed to retrieve the broken tubing sections,forces steel coiled tubing to be retired after a relatively few numberof trips into a well.

Steel coiled tubing has also proven to be subject to expansion afterrepeated uses. Tube expansion results in reduced wall thickness with theassociated reduction in the pressure carrying capability of the steelcoiled tubing. Steel coiled tubing known in the art is typically limitedto an internal pressure up to about 5,000 psi. Accordingly, higherpressure and continuous flexing typically reduces the steel tube'sintegrity and service life.

For example, the present accepted industry standard for steel coiledtube is an A-606 type 4 modified HSLA steel with yield strengths rangingfrom 70 ksi to 80 ksi. The HSLA steel tubing typically undergoesbending, during the deployment and retrieval of the tubing, over radiisignificantly less than the minimum bending radii needed for thematerial to remain in an elastic state. The repeated bending of steelcoiled tubing into and out of plastic deformation induces irreparabledamage to the steel tube body leading to low-cycle fatigue failure.

Additionally, when steel coiled tubing is exposed to high internalpressures and bending loads, the isotropic steel is subjected to hightriaxial stresses imposed by the added pressure and bending loads. Thehigh triaxial stresses result in significant plastic deformation of thetube and diametral growth of the tube body, commonly referred to as“ballooning”. When the steel coiled tube experiences ballooning, theaverage wall thickness of the tube is reduced, and often causes abursting of the steel tube in the area of decreased thickness.

Steel coiled tubes also experience thinning of the tube walls due to thecorrosive effect of materials used in the process of working over thewell and due to materials located on the inner surface of the well bore.The thinning resulting from corrosive effects of various materialscauses a decrease in the pressure and the tensile load rating of thesteel coiled tubing.

It is, therefore, desirable to provide a non-steel coil tubing which iscapable of being deployed and spooled under borehole conditions, whichdoes not suffer from the limitations of steel tubing and is highlyresistant to chemicals.

For the most part, prior art non-metallic tubular structures that aredesigned for being spooled and also for transporting fluids, are made asa hose whether or not they are called a hose. An example of such a hoseis the Feucht structure in U.S. Pat. No. 3,856,052 which haslongitudinal reinforcement in the side walls to permit a flexible hoseto collapse preferentially in one plane. However, the structure is aclassic hose with vulcanized polyester cord plies which are not capableof carrying compression loads or high external pressure loads. Hosestypically use an elastomer such as rubber to hold fiber together but donot use a high modulus plastic binder such as epoxy. Hoses are designedto bend and carry internal pressure but are not normally subjected toexternal pressure or high axial compression or tension loads.

When the ends of a hose are subjected to opposing forces, the hose issaid to be under tension. The tensile stress at any particularcross-section of the hose is defined as the ratio of the force exertedon that section by opposing forces to the cross-sectional area of thehose. The stress is called a tensile stress, meaning that each portionpulls on the other.

With further reference to a hose subjected to opposing forces, the termstrain refers to the relative change in dimensions or shape of the hosethat is subjected to stress. For instance, when a hose is subjected toopposing forces, a hose whose natural length is L0 will elongate to alength L1=L0+Delta L, where Delta L is the change in the length of thehose caused by opposing forces. The tensile strain of the hose is thendefined as the ration of Delta L to L0, i.e. the ratio of the increasein length to the natural length.

The stress required to produce a given strain depends on the nature ofthe material under stress. The ratio of stress to strain, or the stressper unit strain, is called an elastic modulus. The larger the elasticmodulus, the greater the stress needed for a given strain.

For an elastomeric type material, such as used in hoses, the elongationat break is so high (typically greater than 400 percent) and thestress-strain response so highly nonlinear; it is common practice todefine a modulus corresponding to a specified elongation. The modulusfor an elastomeric material corresponding to 200 percent elongationtypically ranges form 300 psi to 2000 psi. In comparison, the modulus ofelasticity for typical plastic matrix material used in a composite tubeis from 100,000 psi to 500,000 psi or greater, with representativestrains to failure of from 2 percent to 10 percent. This largedifference in modulus and strain to failure between rubber and plasticsand thus between hoses and composite tubes is what permits a hose to beeasily collapsed to an essentially flat condition under relatively lowexternal pressure. This large difference also eliminates the hose'scapability to carry high axial tension or compression loads while thehigher modulus characteristic of the plastic matrix material used in acomposite tube is sufficiently stiff to transfer loads into the fibersand thus resist high external pressure and axial tension and compressionwithout collapse.

The procedure to construct a composite tube to resist high externalpressure and compressive loads involves using complex compositemechanics engineering principles to ensure that the tube has sufficientstrength. It has not been previously considered feasible to build atruly composite tube capable of being bent to a relatively smalldiameter, and be capable of carrying internal pressure and high tensionand compression loads in combination with high external pressurerequirements. Specifically a hose will not sustain high compression andexternal pressure loads.

Accordingly, it is one object of this invention to provide an apparatusand method for providing a substantially non-ferrous spoolable tube thatdoes not suffer from the structural limitations of steel tubing and thatis capable of being deployed and spooled under bore hole conditions.

A further object of the invention is to provide a composite coiled tubecapable of working over wells and delivering various chemicals down holequickly and inexpensively.

Another object of the invention includes providing a coiled tubingcapable of repeated spooling and bending without suffering fatiguesufficient to cause fracturing and failing of the coiled tube.

Other objects of the invention include providing a spoolable tubecapable of carrying corrosive fluids without causing corrosion in thespoolable tube, providing a coiled tube having less weight, andproviding a coiled tube capable of withstanding higher internal pressurelevels and higher external pressure levels without loosing tubeintegrity.

These and other objects will be apparent from the description thatfollows.

SUMMARY OF THE INVENTION

The invention attains the foregoing objects by providing a compositecoiled tube that offers the potential to exceed the performancelimitations of isotropic metals currently used in forming coiled tubes,thereby increasing the service life of the coiled tube and extending theoperational parameters of the coiled tube. The composite coiled tube ofthe invention overcomes the disadvantages in present steel coil tubingby providing, among other things, a composite layer that exhibits uniqueanistropic characteristics capable of providing improved burst andcollapse pressures as well as improved tensile strength, compressionload strength, and load carrying capability.

The composite coiled tube of the present invention comprises a compositelayer having fibers embedded in a matrix and an inner liner formed frompolymeric materials or metal. The fibers in the composite layer areoriented to resist internal and external pressure and provide lowbending stiffness. The composite coiled tube offers the potential toexceed the performance limitations of isotropic metals, therebyincreasing the service life of the tube and extending operationalparameters. In addition, the fibers, the matrix, and the liner used inthe composite coiled tube can make the tube impervious to corrosion andresistant to chemicals used in treatment of oil and gas wells or inflowlines.

The service life potential of the composite coiled tube constructed inaccordance with the invention is substantially longer than that ofconventional steel tube when subjected to multiple plastic deformationbending cycles with high internal pressures. Composite coiled tube alsoprovides the ability to extend the vertical and horizontal reach ofexisting concentric well services. In one operation, the compositecoiled tube is deployed as a continuous string of small diameter tubinginto a well bore to perform a specific well bore procedure. When theservice is completed, the small diameter tubing is retrieved from thewell bore and spooled onto a large reel for transport to and from worklocations. Additional applications of coiled composite tube are fordrilling wells, flowlines, as well as for servicing extended reachapplications such as remedial work in wells or flowlines.

In particular, the invention provides for a composite coiled tube havingan inner liner and a composite layer enclosing the inner liner. Thecomposite layer contains three fibers oriented in a triaxial braid. Atriaxial braid structure is formed of three or more fibers braided in aparticular orientation and embedded in a plastic matrix. In a triaxialbraid, a first structural fiber helically or axially extends along thelongitudinal axis of the tube. A second braiding fiber is clockwisehelically oriented relative to the first structural fiber or relative tothe longitudinal axis of the tube. A third braiding fiber iscounter-clockwise helically oriented relative to the first structuralfiber or relative to the longitudinal axis of the tube. In addition, thefirst structural fiber is interwoven with either the second or the thirdor both braiding fibers. The composite coiled tube constructed with thistriaxial braid structure exhibits unique anistropic characteristicshaving enhanced burst pressure characteristics, collapse pressurecharacteristics, increased bending characteristics, tensile loads, andcompression loads.

The composite layer can be constructed with a matrix material having atensile modulus of at least 100,000 psi, a maximum tensile elongation ofat least 5%, and a glass transition temperature of at least 180 DegreesFahrenheit. Increased tube strength can also be obtained by forming alayer having at least 80%, by fiber volume, of the fibers helicallyoriented relative to the longitudinal axis of the tube at an anglebetween 30 and 70 degrees.

In accordance with further aspects of the invention, the composite tubeincludes a liner that serves as a pressure containment member to resistleakage of internal fluids from within the tubing. The inner liner canbe formed of metal or co-extruded composite polymers. The polymersforming the liner can also include homo-polymers or co-polymers. Themetal or polymeric material forming the liner are impermeable to fluids(i.e. gasses and liquids). The inner liner can also include materialsthat are chemically resistive to corrosives.

The liner provides a path for conducting fluids (i.e. liquids and gases)along the length of the composite tube. The liner can transmit fluidsdown hole for operations upon the interior surfaces of the well hole, orthe liner can transmit fluids or gases to hydraulic or pneumaticmachines operably coupled to the composite tube. That is, the liner canprovide a conduit for powering and controlling hydraulic or pneumaticmachines. The composite tube can have one liner or a plurality of linersfor conducting fluids along the length of the composite tube.

The liner can be constructed to have improved mechanical properties thatenhance the bending characteristics, the strength characteristics, andthe pressure characteristics of the coiled composite tube. For example,the liner can have a mechanical elongation of at least 25%, and a melttemperature of at least 250 degrees Fahrenheit. The liner can alsoenhance the pressure characteristics of the composite tube by increasingthe bonding strength between the inner liner and the composite layer.This can be achieved by placing groves on the exterior surface of theliner, such that the grooves can hold matrix material that binds thecomposite layer to the exterior of the liner.

Another feature of the invention includes providing a liner capable ofdissipating static charge buildup. A liner having an additive of carbonblack can prevent static charge buildup. By preventing static chargebuildup, the liner is more likely to prevent the ignition of flammablefluid circulating within the tube.

In a preferred embodiment, the composite layer is formed of three ormore fibers interwoven in a triaxial braid and suspended in a matrixmaterial. For example, the composite layer can comprise a helicallyextending first fiber, a second fiber clockwise extending and helicallyoriented, and a third fiber counter clockwise extending and helicallyoriented. The first, second and third fibers are oriented such that thefirst fiber is interwoven with either the second fiber or the thirdfiber or both. The composite layer can also include additional pliesformed of fiber and matrix. The fibers in the additional plies can havefibers oriented in many ways, including but not limited to, triaxiallybraiding, biaxially braiding, interwoven and filament wound.

Additional aspects of the invention provide for a separate interfacelayer interposed between the liner and the composite layer. Thisinterface layer allows the composite coiled tube to withstand extremepressures inside and outside the tube without causing degradation of thecomposite tube. The interface layer bonds the composite layer to theliner. In addition, the interface layer can serve as a transition layerbetween the composite layer and the liner. For example, the interfacelayer can have a modulus of elasticity between the axial modulus ofelasticity of the liner and the axial modulus of elasticity of thecomposite layer, thereby providing a smooth transition in the modulus ofelasticity between the liner and the composite layer.

Other aspects of the invention include a composite coiled tube having apressure barrier layer. The pressure barrier layer can be locatedexternal to the composite layer for preventing fluids (i.e. gases orliquids) from penetrating into the composite tube. The pressure barrierlayer also prevents external pressure from being directly applied to theouter surface of the inner liner, thereby preventing exterior pressurefrom collapsing the inner liner. The pressure barrier layer can beformed of an impermeable material such as either polymeric film(including polyester), thermoplastic, thermoset film, elastomer ormetallic film. The impermeable material can be helically orcircumferentially wrapped around the composite layer. In addition, thepressure barrier layer can include a fused particle coating. Preferably,the pressure barrier layer has a minimal tensile elongation of 10% andan axial modulus of elasticity of less than 750,000 psi, to aid in theenhanced bending and pressure characteristics of the composite coiledtube.

Further features of the invention provide for a composite tube having anouter protective layer external to the composite layer. The outerprotective layer can provide an outer protective surface and an outerwear resistant surface. The outer protective layer can also resistimpacts and abrasion. In those aspects of the invention having both apressure barrier layer and a outer protective layer, the pressurebarrier layer is typically sandwiched between the composite layer andthe outer protective layer.

An additional feature of the invention is an energy conductor embeddedin the composite tube. The energy conductor extends along the length ofthe composite tube. Energy conductors include electrical medium (such aselectrical wiring), optical medium (such as fiber optics), hydraulicmedium (such as a fluid impermeable tube), and pneumatic medium (such asa gas impermeable tube). The energy conductors can be embedded withinthe liner or within the composite layer of the spoolable composite tube.

Energy conductors commonly have low strain capability and thus can bedamaged easily by large deformations such as those imposed by bending.These energy conductors are thus oriented in a helical directionrelative to the longitudinal axis of the tube. This orientationminimizes the strain on the energy conductor when the tube bends. In analternative aspect of the invention, the energy conductors can bealigned axially along the length of the tube. Two axially aligned energyconductors that are diametrically opposed along the length of the tubecan provide a bending moment along the length of the composite tube,such that the conductors are located on a neutral bending axis thatminimizes bending strains on the conductors.

Various embodiments of the invention exist which include one or moreaspects and features of the invention described above. In oneembodiment, the spoolable composite tube comprises an inner liner and anouter composite layer. In all embodiments, the tube can be designed toinclude or exclude an interface layer sandwiched between the inner linerand the composite layer. The interface layer increases the bondingstrength between the liner and the composite layer. Other embodimentsprovide for a composite tube including a liner, a composite layer, and apressure barrier. Further embodiments include a liner, a compositelayer, a pressure barrier, and an external protective layer. While in anadditional embodiment, the composite tube might include only a liner, acomposite layer, and a pressure barrier. The invention also contemplatesa spoolable tube having a liner, an inner composite layer, a pressurebarrier, and an outer composite layer surrounding the pressure barrier.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be obtained byreference to the drawings in which:

FIG. 1 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention that includes a liner and acomposite layer;

FIG. 2 is a side view of a flattened out composite layer, constructedaccording to the invention, that has triaxially braided fiber componentsand which is suitable for constructing the composite layer of thecomposite tube shown in FIG. 1;

FIG. 3 is a cross-sectional view of the composite coiled tube having aninner liner surrounded by multiple composite layers;

FIG. 4 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention having a liner, an interfacelayer, and a composite layer;

FIG. 5 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention having a liner, an interfacelayer, a composite layer, and a pressure barrier;

FIG. 6 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention that includes a liner, aninterface layer, a composite layer, a pressure barrier, and an outerprotective layer;

FIG. 7 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention that includes a liner, acomposite layer, and a pressure barrier;

FIG. 8 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention comprising a liner, an innercomposite layer, a pressure barrier, and an outer composite layer;

FIG. 9 is a side view, partially broken away, of a composite coiled tubeconstructed according to the invention that includes an energyconductor; and

FIG. 10A is a cross-sectional view of the composite tube of FIG. 9having an axially extending energy conductor embedded in the liner;

FIG. 10B is a cross-sectional view of the composite tube of FIG. 9having an axially extending energy conductor embedded in the compositelayer;

FIG. 10C is a cross-sectional view of the composite tube of FIG. 9having an axially extending energy conductor embedded between the linerand the composite layer;

FIG. 11 is a cross-sectional view of the composite tube of FIG. 9 havinga composite layer enclosing the liner and the energy conductor; and

FIG. 12 illustrates the bending events that occur when running coiledtubing in and out of a well bore.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Composite fibers (graphite, Kevlar, fiberglass, boron, etc.) havenumerous assets including high strength, high stiffness, light-weight,etc., however, the stress strain response of composite fibers is linearto failure and therefore non ductile. Composite coiled tubing musttherefore address the strain limitations in another manner, i.e., byproviding a construction to meet the requirements with a near elasticresponse or with large deformations of the matrix. Such a compositearrangement must have high resistance to bending stresses and internalpressure and external pressure. It must also have high axial stiffness,high tensile and compressive strength and be resistant to shear stress.All of these properties are combined in the composite tubular member ofthe invention to provide a coiled tubing which can be bent to a radiuscompatible with winding onto a reasonable size spool.

P. K. Mallick in the text book entitled Fiber-Reinforced Composites,Materials, manufacturing and Design, defines a composite in thefollowing manner: “Fiber-reinforced composite materials consist offibers of high strength and modulus embedded in or bonded to a matrixwith distinct interfaces (boundary) between them. In general, fibers arethe principal load-carrying member, while the surrounding matrix keepsthem in the desired location and orientation, acts as a load transfermedium between them, and protects them from environmental damages due toelevated temperatures and humidity, for example”. This definitiondefines composites as used in this invention with the fibers selectedfrom a variety of available materials including carbon, aramid, andglass and the matrix or resin selected from a variety of availablematerials including thermoset resin such as epoxy and vinyl ester orthermoplastic resins such as polyetheretherketone (PEEK),polyetherketoneketone (PEKK), nylon, etc. Composite structures arecapable of carrying a variety of loads in combination or independently,including tension, compression, pressure, bending, and torsion.

Webster's Ninth New Collegiate Dictionary defines hose as “a flexibletube for conveying fluids”. By comparison, a hose is distinctlydifferent from a composite tube. Hose products such as umbilical linesused in subsea application are constructed of high strength fibers suchas aramid, dacron, or nylon laid down in a geodesic pattern onto asubstrate plastic liner tubular structure. Alternatively, a hose may beconstructed of high strength fibers with a low modulus binder such asrubber. In either case, a hose is designed to carry pressure loads andto exhibit good bending flexibility, but a hose has very limited abilityto carry compressive, tension and torsion loads or external pressure.

The composite tube described in this invention cannot only carry highinternal pressure but can also carry high compressive, tension andtorsion loads, independently or in combination. Such capability isessential if the tubing is to be used for applications such as coiledtubing in which the tubing is pushed into a high pressure reservoir andto overcome the friction to movement within the well bore, especiallyfor highly deviated or horizontal wells. In addition, the tube isrequired to carry its own weight as it is suspended for 20,000-feet ormore in a well bore and to be able to have high pulling capability toextract tools or to overcome being struck from sand and circulatingsolids which have collapsed around the tube. Such loads in the case ofcoiled tubing in deep wells can be in excess of 20,000 pounds. In otherapplications the tubing must also be capable of carrying high torsionloads. It was not considered feasible until the development representedin the current patent application, that one could design and build acomposite tube capable of being bent to a relatively small diameter suchas required for coiled tubing spooling and simultaneously be capable ofcarrying internal pressure and other loads.

In forming composite structures, several well known techniques may beused such as pultrusion, fiber winding, braiding and molding. Inpultrusion, fibers are drawn through a resin impregnating apparatus,then through dies to provide the desired shape. Alternatively, the resinmay be injected directly within the die. Heat forming and curingstructures are provided in conjunction with the dies. In fiber winding,the various layers forming the composite structure are each formed bywinding or wrapping fibers and a polymer matrix around a mandrel or someother underlying structure that provide a desired shape. Successivecomposite layers can then be applied to underlying composite layers. Atriaxial braiding structure can be manufactured using the fiber windingtechniques disclosed in Quigley, U.S. Pat. No. 5,188,872 and in Quigley,U.S. Pat. No. RE 35,081.

FIG. 1 illustrates a composite coiled tube 10 constructed of an innerliner 12 and a composite layer 14. The composite coiled tube isgenerally formed as a member elongated along axis 17. The coiled tubecan have a variety of tubular cross-sectional shapes, includingcircular, oval, rectangular, square, polygonal and the like. Theillustrated tube has a substantially circular cross-section.

Liner 12 serves as a pressure containment member to resist leakage ofinternal fluids from within the composite coiled tube 10. In oneembodiment the liner 12 is metallic, and in an alternative embodimentthe liner 12 is formed of polymeric materials having an axial modulus ofelasticity exceeding 100,000 psi. A liner having a modulus exceeding100,000 psi is preferable as it is indicative of a tube capable ofcarrying high axial tension that does not cause the tube to compress orbreak. In addition, a liner with an axial modulus of elasticity lessthan 500,000 psi advantageously allows the liner to bend, rather thanpull away from the composite layer, as the composite tube is spooled orbent around a reel.

In the case of a metal liner, the metals forming the liner can include,individually or in combination, steel, copper, or stainless steel. Inthe case of a polymeric liner, the polymeric materials making up theliner 12 can be thermoplastic or thermoset materials. For instance, theliner can be formed of homo-polymers, co-polymers, composite polymers,or co-extruded composite polymers. Homo-polymers refer to materialsformed from a single polymer, co-polymers refers to materials formed byblending two or more polymers, and composite polymers refer to materialsformed of two or more discrete polymer layers that have been permanentlybonded or fused. The polymeric materials forming the inner liner arepreferably selected from a group of various polymers, including but notlimited to: polyvinylidene fluoride, etylene tetrafluoroethylene,cross-linked polyethylene (“PEX”), polyethylene, and polyester. Furtherexemplary thermoplastic polymers include materials such as polyphenylenesulfide, polyethersulfone, polyethylene terephthalate, polyamide,polypropylene, and acetyl.

Liner 12 can also include fibers to increase the load carrying strengthof the liner and the overall load carrying strength of the spoolablecomposite tube 10. Exemplary composite fibers include graphite, kevlar,fiberglass, boron, and polyester fibers, and aramid.

The liner 12 can be formed to be resistive to corrosive chemicals suchas heterocyclic amines, inorganic sulfur compound, and nitrogenous andacetylenic organic compounds. Three types of liner material,polyvinylidene fluoride (“PVDF”), etylene tetrafluoroethylene (“ETFE”),and polyethylene (“PE”), have been found to meet the severe chemicalexposure characteristics demanded in particular applications involvingcomposite coiled tubing. Two particularly attractive materials for theliner are the RC10-089 grade of PVDF, manufactured by Atochem, andTefzel® manufactured DuPont.

In other embodiments of liner 12, the liner comprises co-polymers formedto achieve enhanced liner characteristics, such as corrosion resistance,wear resistance and electrical resistance. For instance, a liner 12 canbe formed of a polymer and an additive such that the liner has a highelectrical resistance or such that the liner dissipates static chargebuildup within the composite tube 10. In particular, carbon black can beadded to a polymeric material to form a liner 12 having a resistivity onthe order of 10⁸ ohms/centimeter. Accordingly, the carbon black additiveforms a liner 12 having an increased electrical conductivity thatprovides a static discharge capability. The static discharge capabilityadvantageously prevents the ignition of flammable fluids beingcirculated within the composite coiled tube 10.

In a further aspect of the invention, the liner 12 has a mechanicalelongation of at least 25%. A liner with a mechanical elongation of atleast 25% can withstand the increased bending and stretching strainsplaced upon the liner as it is coiled onto a reel and inserted into andremoved from various well bores. Accordingly, the mechanical elongationcharacteristics of the liner prolong the overall life of the compositecoiled tube 10. In addition, the liner 12 preferably has a melttemperature of at least 250° Fahrenheit so that the liner is not alteredor changed during the manufacturing process for forming the compositecoiled tubing. A liner having these characteristics typically has aradial thickness in the range of 0.02-0.25 inches.

The liner can act as a vehicle for transmitting chemicals that act uponthe interior of the well bore, and the liner can also provide a conduitfor transmitting fluids that power or control machines operably coupledwith the composite tube. When the liner acts as a hydraulic controlline, the liner diameter is typically less than ½ inch. The diameter ofthe liner can vary, as can the number of liners within the compositetube. For example, the liner can include a plurality of tubes fortransmitting different fluids through the composite tube.

The composite layer 14 can be formed of a number of plies, each plyhaving a fibers disposed with a matrix, such as a polymer, resin, orthermoplastic. The fibers typically comprise structural fibers andflexible yarn components. The structural fibers are formed of eithercarbon, nylon, polyester, aramid, thermoplastic, or glass. The flexibleyarn components, or braiding fibers, are formed of either nylon,polyester, aramid, thermoplastic, or glass. The fibers included in layer14 can be woven, braided, knitted, stitched, circumferentially wound, orhelically wound. In particular, the fibers can be biaxially ortriaxially braided. The composite layer 14 can be formed throughpultrusion processes, braiding processes, or continuous filament windingprocesses. A tube formed of the liner 12 and the composite layer 14 forma composite tube having a maximum tensile strain of at least 0.25percent and being capable of maintaining an open bore configurationwhile being spooled on a reel.

The liner 12, illustrated in FIG. 1, can also include grooves 15 orchannels on the exterior surface of the liner. The grooves increase thebonding strength between the liner 12 and the composite layer 14 bysupplying a roughened surface for the fibers in the composite layer 14to latch onto. The grooves can further increase the bonding strengthbetween the liner 12 and the composite layer 14 if the grooves arefilled with a matrix. The matrix acts as a glue, causing the compositelayer to be securely adhered to the underlying liner 12. Preferably, thegrooves are helically oriented on the liner relative to the longitudinalaxis 17.

FIG. 2 shows a “flattened out” view of a preferred composite layer 14having a fiber component 20 interwoven with a plurality of like ordifferent fiber components, here shown as a clockwise helically orientedfiber component 16 and a counterclockwise helically oriented fibercomponent 18. The configuration of layer 14 shown in FIG. 2, isappropriately denoted as a “triaxially braided” ply. The fibercomponents 16, 18, 20 are suspended in a matrix 22.

Helically oriented fibers are fibers that follow a spiral path.Typically, helical fibers spiral around a mandrel underlying thecomposite tube or they spiral around underlying layers of the compositetube. For example, a helically oriented fiber follows a path comparableto the grooves around the shaft of a common screw. A helical fiber canbe described as having an axial vector, an angle of orientation, and awrapping direction. The axial vector indicates that the helical fibercan follow a path along the length of the tube 10 as it spirals aroundthe tube, as opposed to a fiber that continually wraps around aparticular section of the tube 10 without extending along the length ofthe tube. The angle of orientation of the helical fiber indicates thehelical fiber's angle relative to a defined axis, such as thelongitudinal axis 17. For example, a helical fiber having an angle of 0degrees is a fiber that extends parallel to the longitudinal axis andthat does not wrap around the tube 10, while a fiber having an angle of90 degrees circumferentially wraps around the tube 10 without extendingalong the length of the tube. The wrapping direction of the helicalfiber is described as either clockwise or counter-clockwise wrappingaround the tube 10.

The fiber components can be formed of carbon, glass, aramid (such askevlar® or twaron®, thermoplastic, nylon, or polyester. Preferably,fibers 16 and 18 act as braiding fibers and are formed of either nylon,polyester, aramid, thermoplastic, or glass. Fiber 20 acts as astructural fiber and is formed of either carbon, glass, or aramid. Fiber20 increases the axial strength of the composite layer 14 and thespoolable tube 10.

The matrix material 22 is generally a high elongation, high strength,impact resistant polymeric material such as epoxy. Other alternativematrixes include nylon-6, vinyl ester, polyester, polyetherketone,polyphenylen sulfide, polyethylene, polypropylene, and thermoplasticurethanes.

Fiber 20 extends helically or substantially axially relative to thelongitudinal axis 17. The helically oriented fiber component 16 and 18tend to tightly bind the longitudinal fiber component 20 with the matrixmaterial 22 in addition to providing increased bending stiffness alongaxis 17 and increased tortional strength around axis 17. The helicallyoriented fiber components 16 and 18 can be interwoven amongstthemselves. To this end, successive crossings of two fiber components 16and 18 have successive “over” and “under” geometries.

According to a preferred aspect of the invention, the composite layerincludes a triaxial braid that comprises an axially extending fibercomponent 20, a clockwise extending second fiber component 16 and acounter-clockwise extending third fiber component 18, wherein the fiber20 is interwoven with either fiber 16 or fiber 18. Each helicallyoriented fiber 16, 18 can therefor be considered a braiding fiber. Incertain aspects of the invention, a single braiding fiber, such as fiber16 binds the fiber component of a given ply together by interweaving thebraiding fiber 16 with itself and with the axially extending fiber 20. Afiber is interwoven with itself, for example, by successively wrappingthe fiber about the member and looping the fiber with itself at eachwrap.

In another aspect of the invention, axially extending structural fiber20 is oriented relative to the longitudinal axis 17 at a first angle 28.Typically, fiber 20 is helically oriented at the first angle 28 relativeto the longitudinal axis 17. The first angle 28 can vary between 5°-20°,relative to the axis. The first angle 28 can also vary between 30°-70°,relative to the axis 17. Although it is preferred to have fiber 20oriented at an angle of 45° relative to axis 17.

The braiding fiber 16 is oriented relative to structural fiber 20 at asecond angle 24, and braiding fiber 18 is oriented relative tostructural fiber 20 at a third angle 26. The angle of braiding fibers 16and 18, relative to structural fiber 20, may be varied between ±10° and±60°. In one aspect of the invention, fibers 16 and 18 are oriented atan angle of ±20° relative to fiber 20.

One failure mechanism of the composite tube during loading, especiallyunder bending/pressure and tension and compression loading, is believedto be the development of micro-cracks in the resin and the introductionof microscopic defects between fibers. The development of somemicro-cracks is also believed to be inevitable due to the severe loadsplaced on the tube during the manufacturing and bending of the tube.However, the effects of these micro-cracks and microscopic defects canbe retarded by restraining the growth and accumulation of themicro-cracks and microscopic defects during the manufacturing and use ofthe composite coiled tube. The applicants have discovered that theselection of fibers 16 and 18 from the group of fibers consisting ofnylon, polyester, glass and aramid mitigates and stops the growth of themicroscopic defects. Thus, the selection of fibers 16 and 18 from theparticularly noted materials improves the damage tolerance and fatiguelife of the composite coiled tubing 10.

Applicant has further determined that the total volume of any particularfibrous material in any selected layer of the composite coiled tubeaffects the overall mechanical characteristics of the composite coiledtube 10, including a reduction in crack propagation. It additionallyfollows that the total volume of any particular fibrous material in thewhole composite coiled tube also affects the mechanical characteristicsof the composite coiled tube 10. A composite coiled tube having improvedstrength and durability characteristics is obtained by forming acomposite layer 14 wherein the combined fiber volume of the clockwiseextending and counter-clockwise extending braiding fibers 16 and 18constitute less than 20% of the total fiber volume in the compositelayer 14. Further in accordance with this embodiment, the fiber volumeof the axially extending fiber 20 should constitute at least 80% of thefiber volume of the composite layer 14. Preferably, the first compositelayer 14 includes at least 80% by fiber volume of substantiallycontinuous fibers oriented relative to the longitudinal axis 17 of thetube at an angle between 30-70 degrees.

When the matrix 20 is added to composite layer 14, the volume of matrixin the layer 14 typically accounts for 35% or more of the volume in thecomposite layer 14. Accordingly, the combined volume of all the fibersin composite layer 14 account for less than 65% of the volume of thecomposite layer 14. It is thus evident, that the volume of fibers 16 and18 account for less than 13% of the total volume of the composite layer14 and that the volume of fiber 20 accounts for at least 52% of thetotal volume of the composite layer 14.

Matrix 20 in composite layer 14 is selected such that transverse shearstrains in the laminar can be accommodated without breaching theintegrity of the coil composite tube 10. The strains generally is theresult of bending the spoolable composite tube over the reel. Thesestrains do not impose significant axial stresses on the fiber, but theydo impose significant stresses on the matrix 20. Accordingly, matrix 20should be chosen such that the maximal tensile elongation is greaterthan or equal to 5%. The Applicant has further shown that choosing amatrix having a tensile modulus of at least 100,000 psi adds to theability of the coil composite tube to withstand excessive strain due tobending. In accordance with the further aspect of the invention, thematrix 20 also has a glass transition temperature of at least 180°Fahrenheit so that the characteristics of the resin are not alteredduring high temperature uses involving the coiled composite tube 10. Thetensile modulus rating and the tensile elongation ratings are generallymeasured as the coil composite tube is being manufactured at 70°Fahrenheit. Matrix materials having these characteristics include epoxy,vinyl ester, polyester, urethanes, phenolics, thermoplastics such asnylon, polyropelene, and PEEK.

FIG. 3 illustrates a coiled composite tube 10 having an inner liner 12and a first composite layer 14A, a second composite layer 14B, and athird composite layer 14C. Each of the composite layers is formed offibers embedded in a matrix, and each of the composite layerssuccessively encompasses and surrounds the underlying composite layer orliner 12. At least one of the composite layers, 14A, 14B, 14C, includesa helically oriented fiber in a matrix. Preferably, at least one of thecomposite layers 14A, 14B, 14C, contains a ply as described in FIG. 2.In particular, one of the composite layers 14A, 14B, 14C, has a firsthelically extending fiber, a second clockwise extending fiber, and athird counterclockwise extending fiber wherein the first fiber isinterwoven with at least one of the second and third fibers. The othertwo composite layers contain fiber suspended in a matrix. The fibers canbe axially extending, circumferentially wrapped, or helically wrapped,biaxially braided or triaxially braided.

According to one aspect of the invention, the fibers in each of thecomposite layers are all selected from the same material. In otheraspects of the invention, the fibers in each of the composite layers areall selected from the different materials. For example, composite layer14A can comprise a triaxially braided ply having clockwise andcounter-clockwise helically oriented fibers formed of polyester andhaving a helically extending fiber formed of glass; composite layer 14Bcan comprise a ply having a circumferentially wound kevlar fiber; andcomposite layer 14C can comprise a triaxially braided ply having aclockwise and counter-clockwise helically oriented fibers formed ofglass and having a helically extending fiber formed of carbon.

The Applicant's have discovered that additional composite layers, beyondthe initial composite layer 14 of FIG. 1, enhance the capabilities ofthe coiled composite tube. In particular, the interaction between theadditional composite layers creates a synergistic effect not found in asingle composite layer. The Applicant discovered that composite layershaving carbon fibers carry proportionately more of the load as thestrain in the coiled composite tube 10 increases, as compared to anequivalent design using glass fibers or aramid fibers. While a compositelayer using kevlar (i.e. aramid) fibers provide excellentpressure/cyclical bending capabilities to the coiled composite tube 10.The kevlar fibers appear to have a weakness when compared to the carbonfibers in compressive strength. Accordingly, a coiled composite tube 10incorporating both kevlar and carbon fibers provides a compositestructure having improved characteristics not found in compositestructures having composite layers formed of only carbon fibers or onlykevlar fibers.

Accordingly, one aspect of the invention incorporates a composite layer14A formed of carbon fibers and polyester fibers in a triaxially braidedstructure and a second composite layer 14B formed of kevlar fibers. Thekevlar fibers can be incorporated into either a conventional bi-axialbraid, triaxial braid, or helical braid. For instance, the secondcomposite layer can include two sets of aramid fibers bi-axially braidedtogether. The coiled composite tube 10 having an inner composite layer14A formed with carbon fibers and an exterior composite layer 14B formedwith kevlar fibers provides a coiled composite tube having balancedstrength in two directions and provides a coiled composite tube having aconstricting force which helps restrain the local buckling ofdelaminated sublamina and subsequent delamination growth, therebyimproving the fatigue resistance of the coiled composite tube 10.Certainly, this aspect of the invention can include a third compositelayer 14C external to the second composite layer 14B. The thirdcomposite layer 14C can, for instance, include a matrix and a fiberhelically oriented relative to the longitudinal axis 17.

In another aspect of the invention, as illustrated in FIG. 3, thecomposite layer 14A comprises a triaxially braided ply having an axiallyextending fiber formed of carbon and having a clockwise extending fiberand a counter-clockwise extending fiber both formed of polyester. Inaddition, the helically extending fiber 20 is oriented at an 45° angleto the axis of the coiled composite tube 10. Further in accordance withthis embodiment, composite layer 14B is triaxially braided and comprisesa helically extending fiber formed of carbon and oriented at an angle of45° relative to the axis 17 of coiled composite tube 10. Composite layer14B further includes a clockwise extending second fiber and acounter-clockwise extending third fiber formed of polyester. The thirdcomposite layer 14C, is biaxially braided, and comprises a kevlar fiberextending helically and oriented at a 54° angle to the axis 17 of thecomposite coiled tube 10.

FIG. 4 illustrates a composite coiled tube elongated along an axis 17and having an inner liner 12, an interface layer 56, and a compositelayer 14. The interface layer 56 surrounds the liner 12 and issandwiched between the liner 12 and the composite layer 14. Theinterface layer 56 improves the bonding between the inner liner 12 andthe composite layer 14.

It is important in the composite coiled tubing 10 that the liner 12 beintegrally attached to the composite layer 14. The necessity for abonded liner is that in certain operating conditions experienced in downhole service, the external surface of the tube will be subjected tohigher pressure than the interior of the tube. If the liner is notbonded to the composite layer 14 this external pressure could force theliner to buckle and separate from the composite layer such that theliner collapses. In addition, loading and bending of the tube mayintroduce microscopic cracks in the composite layer 14 which could serveas microscopic conduits for the introduction of external pressure to beapplied directly to the outer surface of the liner 12. Once again, theseexternal pressures could cause the liner 12 to collapse. The interfacelayer 56 provides a mechanism for bonding the liner 12 to the compositelayer 14 such that the liner does not collapse under high externalpressures. The interface layer 56 can also reduce cracking and thepropagation of cracking along the composite layer 14 and liner 12.

In accordance with one aspect of the invention, the interface layer 56comprises a fiber reinforced matrix where the fiber volume is less than40% of the total volume of the interface layer 56. The matrix and thefiber forming interface layer 56 predominately act as an adhesive layerthat bonds the liner 12 to the composite layer 14. The fibers within theinterface layer 56 can be oriented in various ways, including a woven ornon-woven structure. Preferably, the fibers within the interface layer56 are polyester fibers. An interface layer having this structure isable to prevent the liner from separating from the composite layer evenwhen the differential pressure between the exterior and interior of thetube 10 exceeds 1,000 psi.

The matrix within the interface layer 56 can comprise a filled polymericlayer or an unfilled polymeric layer. A filled polymeric layer uses apolymeric matrix having additives that modify the properties of thepolymeric layer. The additives used in the filled polymeric layerinclude particulates and fibers. For instance, carbon black powder canbe added to the polymeric layer to increase the conductivity of theinterface layer 56, or chopped glass fibers can be added to thepolymeric layer to increase the stiffness of the interface layer 56.

According to a further embodiment of the invention, the interface layerhas an axial modulus of elasticity that lies between the modulus of theelasticity of the liner 12 and the modulus of elasticity of thecomposite layer 14. The interface layer 56 thus has a modulus ofelasticity that transitions between the modulus of elasticity of theliner 12 and the composite layer 14. By providing a transitional modulusof elasticity, the interface layer aids in preventing the liner 12 frompulling away from the composite layer 14 during the bending action ofthe composite coiled tube 10.

The interface layer 56 furthermore increases the fatigue life of thecoiled composite tube 10. The structure of the interface layer 56achieves this by dissipating shear stress applied along the length ofthe coiled composite tube 10. By dissipating the shear, the interfacelayer reduces cracking and the propagation of cracks along the compositelayer 14.

FIG. 5 illustrates a composite coiled tube elongated along an axis 17and having an inner liner 12, an interface layer 56, a composite layer14, and a pressure barrier layer 58. The pressure barrier layer 58prevents gases or liquids (i.e. fluids) from penetrating into thecomposite coiled tube 10.

It is important for two reasons that fluids not penetrate into thecomposite layer 14. First, a fluid that penetrates through the tube 10to liner 12 can build up to a sufficient level of pressure capable ofcollapsing the liner 12. Second, a fluid that penetrates the coiledcomposite tube 10 during exposure in the well bore 36 may outgas whenthe coil composite tube 10 is returned to atmospheric pressure.

Accordingly, a coiled composite tube 10 can function effectively withouta pressure barrier layer 58 under certain conditions. For example, whenmicro-fractures and defects in the composite layer 14 do not develop toa size that allows fluids to penetrate the composite layer 14, apressure barrier layer is not necessary. However, when micro-fracturesand passages through the composite layer 14 do allows for the migrationof fluids the use of a pressure barrier layer 58 is preferred. Asillustrated in FIG. 5, the pressure barrier layer 58 generally ispositioned outside of the composite layer 14.

The pressure barrier layer 58 can be formed of a metal, thermoplastic,thermoset films, or an elastomer such as a rubber sheet. All thesevarious materials can function as a pressure barrier because theysubstantially prevent the diffusion of fluids. Preferable properties ofthe pressure barrier layer include low permeability to fluids (i.e.,gases or liquids), high elongation, and bondability to composite layer14. It is also preferred that the pressure barrier layer 58 have amaximum tensile elongation of 10% and an axial modulus of elasticity ofless than 750,000 psi. These values of tensile elongation and modulus ofelasticity are measured at 70° Fahrenheit during the manufacturing ofthe coiled composite tube 10. The permeability of the pressure barrierlayer should be less than 0.4×10 to the −10 ccs per sec-cm²-cm-cmhg.

The impermeable pressure barrier layer 58 can be formed of animpermeable films formed of metals or polymers. For instance, acceptablepolymeric films include films formed of polyester, polyimide, polyamide,polyvinyl fluoride, polyvinylidene fluoride, polyethylene, andpolypropylene, or other thermoplastics.

The impermeable film of layer 58 can be a seamless polymer layer whichis coextruded or formed via a powder deposition process. Alternatively,the impermeable film can be helically wrapped or circumferentiallywrapped around the composite layer to form an overlapping and completebarrier. That is, the fiber or material forming the pressure barrierlayer must be wrapped in such a fashion that no gaps exist and thepressure barrier layer 58 is sealed.

Another aspect of the invention provides for a pressure barrier layer 58having a fused particle coating. A fused particle coating is formed bygrinding a polymeric material into a very fine powder. The fine power isthen heat-fused onto the other materials forming the pressure barrierlayer 58 or onto the underlying composite layer 14.

FIG. 6 illustrates a composite coiled tube elongated along an axis 17and having an inner liner 12, an interface layer 56, a composite layer14, a pressure barrier layer 58 and an outer protective layer 60. Theinterface layer 56 enhances the bond between the composite layer 14 tothe inner liner 12. The pressure barrier layer 58 prevents fluids frompenetrating into the composite coiled tube 10. The outer protectivelayer 60 provides wear resistance, impact resistance, and an interfacelayer for the coupling for the coiled composite tube 10. The protectivelayer is positioned such that it surrounds the pressure barrier 58.

Outer protective layer 60 provides abrasion resistance and wearresistance by forming an outer surface to the coil composite tube thathas a low co-efficient of friction thereby causing objects to slip offthe coiled composite tube. In addition, the outer protective layer 60provides a seamless layer for holding the inner layers of the coiledcomposite tube together. The outer protective layer can be formed of afilled or unfilled polymeric layer. Alternatively, the outer protectivelayer 60 can be formed of a fiber, such as kevlar or glass, and amatrix. The fibers of the outer protective layer 60 can be woven in amesh or weave pattern around the inner layers of the coiled compositetube 10, or the fibers can be braided or helically braided around theinner layers of tube 10. In either case, the fibers in the outerprotective layer are wrapped helically around the inner layers of thecoiled composite tube 10 in order to provide a seamless structure.

It has further been discovered by the Applicant that particles can beadded to the outer protective layer to increase the wear resistance ofthe outer protective layer 60. The particles used can include any of thefollowing, individually or in combination with one another: ceramics,metallics, polymerics, silicas, or fluorinated polymers. Adding Teflon®D(MP 1300) particles and an aramid powder (PD-T polymer) to the matrix ofthe outer protective layer 60 has been found to be one effective way toreduce friction and enhance wear resistance.

In the case where the outer protective layer includes fibers, theparticles added to the outer protective layer 60 are such that theyconsist of less than 20% by volume of the matrix. In the case where theouter protective layer does not contain fiber, a particulate such asTeflon® MP 1300 can also be added to the polymeric protective layer.When the outer layer 60 does not include fiber, the particles typicallycomprise less than 60% by coating volume of the outer wear resistantlayer 60.

FIG. 7 illustrates an embodiment of the composite coiled tube elongatedalong an axis 17 and having a liner 12, a composite layer 14, and apressure barrier 58. FIG. 7 is similar to FIG. 5, except that it lacksthe interface layer 56. Particularly, the inner liner 12 is positionedinternally to the composite layer 14, and the composite layer 14 ispositioned internally to the pressure barrier 58. This figureillustrates, among other things, that the interface layer 56 can eitherbe included or removed from all embodiments of the invention, dependingupon whether the circumstances require the use of an interface layer toincrease the bonding strength between the liner and the composite layer.

FIG. 8 illustrates another embodiment of a composite coiled tubeelongated along an axis 17, the composite tube includes a liner 12, afirst composite layer 14, a pressure barrier 58, and a second compositelayer 14′. In this embodiment, the first composite layer 14 surroundsthe internal liner, and the pressure barrier surrounds the firstcomposite layer 14. In addition, the second composite layer 14′surrounds the pressure barrier 58. Particularly, the pressure barrier issandwiched between two composite layers 14 and 14′.

Composite layer 14′ can be structured in any manner that composite layer14 can be structured, but the layers 14 and 14′ need not be identical.In addition, either composite layer 14 or composite layer 14′ caninclude multiple composite layers as illustrated in FIG. 3. The externalcomposite layer 14′ proves useful in providing an exterior surfacecapable of engaging a coupling device.

The external composite layer 14′ can also be fashioned to act as anouter protective layer capable of providing abrasion resistance and wearresistance. This can be achieved by forming the external composite layer14′ from a filled or unfilled polymeric layer. The layer 14′ can alsoachieve increased abrasion and wear resistance by helically wrapping orbraiding those fibers forming composite layer 14′ around the innerlayers of the tube 10. Furthermore, the external composite layer 14′ canbe fashioned to reduce the friction of the exterior of tube 10 by addingparticles to the external composite layer 14′. The particles can includeceramics, metallics, polymerics, silicas, or fluorinated polymers.

FIG. 9 illustrates a composite coiled tube elongated along an axis 17wherein the composite tube includes a liner 12, a composite layer 14,and an energy conductor 62 forming part of the composite layer 14. Theenergy conductor provides a path for passing power, communication orcontrol signals from the surface down through the tube to a machineattached to the end of the tube.

The energy conductor 62 can be either a hydraulic medium, a pneumaticmedium, an electrical medium, an optical medium, or any material orsubstance capable of being modulated with information data or power. Forexample, the energy conductor can be a fluid impermeable tube forconducting hydraulic or pneumatic energy along the length of thecomposite tube. The hydraulic or pneumatic energy can be used to controlor power the operation of a machine, such as a submersible pump,operably coupled to the composite tube. Alternatively, the energyconductor can be an electrically conductive medium, such as copper wire,for transmitting a control or power signal to a machine operably coupledto the composite tube. The energy conductor also includes opticalmedium, such as fiber optics, for transmitting an optical signal alongthe composite tube. The composite tube can include one or more of thedescribed energy conductors.

The hydraulic control line embodiment of the energy conductor 62 used inthe composite tube 10 can be either formed of metal or of a polymericmaterial. In the case of a metal control line, the metals forming thehydraulic line can include, individually or in combination, steel,copper, or stainless steel. Hydraulic control lines typically have adiameter less than ½ an inch. In the case of a polymeric hydraulic line,the polymeric materials making up the hydraulic line can bethermoplastic or thermoset materials. For instance, the hydraulic linecan be formed of homo-polymers, co-polymers, composite polymers, orco-extruded composite polymers. The polymeric materials forming thehydraulic line are preferably selected from a group of various polymers,including but not limited to: polyvinylidene fluoride, etylenetetrafluoroethylene, cross-linked polyethylene (“PEX”), polyethylene,and polyester. Further exemplary thermoplastic polymers includematerials such as polyphenylene sulfide, polyethersulfone, polyethyleneterephthalate, polyamide, polypropylene, and acetyl.

The hydraulic line can also include fibers to increase the load carryingstrength of the hydraulic line and the overall load carrying strength ofthe spoolable composite tube 10. Exemplary composite fibers includegraphite, kevlar, fiberglass, boron, and polyester fibers, and aramid.

The hydraulic line embodiment of the energy conductor 62 can be formedto be resistive to corrosive chemicals such as heterocyclic amines,inorganic sulfur compound, and nitrogenous and acetylenic organiccompounds. Three types of material, polyvinylidene fluoride (“PVDF”),etylene tetrafluoroethylene (“ETFE”), and polyethylene (“PE”), have beenfound to meet the severe chemical exposure characteristics demanded inparticular applications involving composite coiled tubing. Twoparticularly attractive materials for the hydraulic line are theRC10-089 grade of PVDF, manufactured by Atochem, and Tefzel®manufactured DuPont.

In other aspects, the hydraulic line embodiment of the energy conductor62 comprises co-polymers formed to achieve enhanced characteristics,such as corrosion resistance, wear resistance and electrical resistance.For instance, a hydraulic line can be formed of a polymer and anadditive such that the hydraulic line has a high electrical resistanceor such that the hydraulic line dissipates static charge buildup withinthe composite tube 10. In particular, carbon black can be added to apolymeric material to form a hydraulic line having a resistivity on theorder of 10⁸ ohms/centimeter.

The energy conductor 62 can be located in either the liner, thecomposite layers, or the pressure barrier forming the tube 10. But ispreferable to locate the energy conductors in those layers nearest theinterior surface of the tube and not in those layers located near theexterior surface of the tube. If an energy conductor is located near theexterior surface of the tube it is more likely to be subjected tocorrosive surfaces or materials located outside the tube 10. Inaddition, an energy conductor located near the interior of the tube 10will be subjected to smaller bending strains when compared to an energyconductor located near the exterior of the tube.

An energy conductor can be embedded in any of the layers forming thetube 10 using the same methods known in the art for adding a fiber tothe composite layer. In various aspects of the invention, as shown inFIGS. 10A-10C, the energy conductor can be either embedded in: theliner; the composite layer; or between the liner and the compositelayer. In another aspect, as shown in FIG. 11, both the energy conductorand the liner can be surrounded by the composite layer.

Typically, an energy conductor is wound onto a mandrel or any underlyingstructure while applying a matrix. Energy conductors can also be addedto a fiber composite layer with a pultrusion process. For example, theenergy conductor can be drawn through a resin impregnating apparatus,then through dies to provide the desired shape.

A primary concern in placing the conductor 62 in the inner areas of thecomposite tube 10 is to ensure that the bending strains on the conductor62 are minimized. This is particularly critical if the conductor 62 is afiber optic cable. Moreover, the energy conductor 62 can be helicallyoriented relative to the longitudinal axis 17 of the composite tube tominimize the bending strain on conductor 62. The helical orientationallows the compression strain experienced by the section of theconductor located on the interior bend of the tube to be offset by theexpansion strain experienced by the section of the conductor located onthe exterior bend of the tube. That is, the conductor 62 is able tosubstantially distribute the opposing strains resulting from the bendingaction of the composite tube across the length of the conductor 62,thereby preventing irreparable damage to the conductor.

FIG. 10A is a cross-sectional view of the composite tube 10 having anaxially extending energy conductor 62 embedded in the liner 12. Byembedding the conductor 62 solely in the liner, bumps in the outerdiameter of the composite tube potentially formed by the conductor 62are eliminated. In particular, the addition of the conductors 62 to thecomposite tube can cause bumps or ripples in the outer diameter of thecomposite tube as additional layers of material are added over theconductors. These bumps can be substantially eliminated by embedding theconductor 62 in a liner formed of a polymeric material. When formed of apolymeric, the liner envelopes the conductors and cures in a form thatretains a uniform outer diameter.

The conductors can be positioned within the composite tube so that theyextend parallel to the axis of the composite tube 10. By orienting theconductor axially along the length of the tube 10, the conductorsincrease the composite tube's axial stiffness and tensile strength. Theeffect can be increased by orienting a plurality of conductors 62, 62′axially along the length of the tube 10.

As further shown in FIGS. 10A-10C, the conductors 62, 62′ can beoriented so that they are diametrically opposed. This configuration ofthe composite tube 10 creates a major and minor moment of inertia wherethe conductors 62, 62′ are located in a neutral bending axis. Theconfiguration forces a preferred direction of bending upon the tube 10.In effect, the composite tube 10 has a preferred direction for windingonto a spool by bending about the minor moment of inertia. The advantageof this configuration is that high stiffness and high strength materialcan be placed in the inner section of the composite tube 10 withoutsignificant increase in the associated bending strains or sacrifice inthe minimum radius of curvature permitted for spooling. In addition, theplacement of the conductors 62, 62′ on the neutral bending axisminimizes the bending strains on the conductors, thereby minimizingbending damage to the conductors.

FIG. 10B is a cross-sectional view of the composite tube 10 having anaxially extending energy conductor 62 embedded in the composite layer14. Locating the energy conductors in the fiber composite layer mayprove advantageous when the liner 12 is formed of metal. In addition, ittypically proves easier to manufacture a composite tube with the energyconductors embedded in the composite layer 14, rather than beingembedded in the liner 12.

FIG. 10C is a cross-sectional view of the composite tube 10 having anaxially extending energy conductor 62 embedded between the liner 12 andthe composite layer 14.

FIG. 11 is a cross-sectional view of the composite tube 10 having theenergy conductor 62 and the liner 12 enclosed within the composite layer14. This aspect of the invention proves particularly important whenmultiple energy conductors, as shown in FIG. 11, are required. Designshaving multiple energy conductors, or having energy conductors withlarge diameters, require much of the space within the composite tube forthe placement of the energy conductors. As a result, it becomes lessdesirable to embed the energy conductors directly in either the liner orthe composite layer. Accordingly, the energy conductors and the linerare both surrounded by the composite layer. As further illustrated inFIG. 11, the composite layer can be enclosed within a pressure barrier58 and within an outer protective layer 60.

The spaces formed between the energy conductor and the liner are filledwith a fill material 66. The spaces arise when the energy conductor andthe liner do not completely fill the channel within the composite layer14. The fill material can be formed of a polymeric material, such as athermoset or thermoplastic. The polymeric material can be formed ofco-polymers, homo-polymers, or composite polymers. In addition, the fillmaterial can include fibers for added structural strength. The fillmaterial binds the energy conductors and the liner to the compositelayer. In addition, the fill material provides structural support to theenergy conductors and the liner.

FIG. 11 also shows an insulating sheath surrounding the energy conductor62. The insulating sheath insulates the energy conductor fromdetrimental external conditions. For instance, in the case of anelectrical conductor, the insulating sheath 64 electrically insulatesthe energy conductor. The insulating sheath can also be fluidimpermeable for protecting an underlying electrical conductor from thecorrosive effects of external fluids or gases. In the case of opticalconductors, the insulating sheath provides an opaque surface forpreventing the distortion of optical signals within the energy conductor62.

In another aspect of the invention, the energy conductors can include aplurality of energy conductors for powering a machine operably coupledto the coiled tube. For instance, the composite tube 10 can includethree electrical energy conductors that provide a primary line, asecondary line, and a tertiary line for electrically powering a machineusing a three-phase power system. As further illustrated, the compositetube 10 can also include a plurality of liners for transmitting fluidsalong the length of the tube 10.

FIG. 12 illustrates the bending cycles that a coiled composite tube 10is subjected to when performing a typical coiled tubing service. Thetubing 10 is inserted and removed from a well bore 36 located below theground surface. A reel 42 is provided on the surface and the compositecoiled tube 10 is stored on the reel 42. An injector assembly 38 islocated on the surface over the well bore 36. Injector assembly 38typically contains a roller belt 40 used to guide the coiled compositetube 10 through the injector assembly 38 into the well bore 36. Thecoiled composite tube 10 typically is subjected to six bending events asit is inserted and removed from the well bore 36. The first bendingevent 44 takes place when the coiled composite tube 10 is pulled off theservice reel 42. When the coiled composite tube 10 reaches the assembly38, the coiled tube passes through two bending events 46 and 48. Thebending events 50, 52 and 54 are the reverse of bending events 44, 46,48 and occur as the coiled composite tube 10 is extracted from the wellbore 36. The insertion and extraction of the tube 10 thus results in atotal of six bending events for every round trip of the coiled compositetube 10. The current steel tubing being used in the field can generallybe cycled three times through the bending events described in FIG. 4 inconjunction with high internal pressures before the steel tubing fails.In comparison, the coiled composite tube of the Applicant's inventioncan be cycled 10,000 times through the bending events described in FIG.4.

It is also to be understood that the following claims are to cover allgeneric and specific features of the invention described herein, and allstatements of the scope of the invention which, as a matter of language,might be said to fall there between.

1. A spoolable tube comprising: an inner liner; a composite layerenclosing said liner and comprising high strength fibers; an outerprotective layer enclosing said composite layer and inner liner; whereinsaid spoolable tube has an open bore configuration when spooled on areel.
 2. The spoolable tube of claim 1, wherein said composite layerfurther includes a glue.
 3. The spoolable tube of claim 1, wherein saidcomposite layer further includes a resin.
 4. The spoolable tube of claim1, wherein said composite layer further includes a polymer.
 5. Thespoolable tube of claim 1, wherein said fibers comprise one or more of:glass, carbon and aramid.
 6. The spoolable tube of claim 5, wherein saidfibers comprise glass.
 7. The spoolable tube of claim 1, wherein saidfibers are helically wound about said inner liner.
 8. The spoolable tubeof claim 1, wherein said fibers include clockwise and counter-clockwisehelically oriented fibers.
 9. The spoolable tube of claim 6, whereinsaid fibers include clockwise and counter-clockwise helically orientedfibers.
 10. The spoolable tube of claim 1, wherein said fibers arehelically wound relative to the longitudinal axis of said tube.
 11. Thespoolabe tube of claim 10, wherein said fibers are helically wound atabout ±30° to about ±70° relative to the longitudinal axis of said tube.12. The spoolabe tube of claim 1, wherein said liner comprises athermoplastic.
 13. The spoolabe tube of claim 1, wherein said liner hasa melt temperature of at least 250° F.
 14. The spoolable tube of claim1, wherein said liner has an axial modulus of elasticity less than500,000 psi.
 15. The spoolable tube of claim 6, wherein said linercomprises at least one of: polyethylene, cross-linked polyethylene,polyamide, polypropylene, polyvinylidene fluoride, and a polyester. 16.The spoolable tube of claim 1, wherein said outer protective layerfurther includes a coupling device.
 17. The spoolable tube of claim 1,further including a coupling device.
 18. The spoolable tube of claim 1,wherein said outer protective layer holds said composite layer together.19. The spoolable tube of claim 18, wherein said outer protective layeris seamless.
 20. The spoolable tube of claim 1, wherein said outerprotective layer is seamless.
 21. The spoolable tube of claim 1, whereinsaid outer protective layer comprises a polymer.
 22. The spoolable tubeof claim 21, wherein said outer protective layer comprises fillers. 23.The spoolable tube of claim 1, further including a pressure barrierlayer.
 24. The spoolable tube of claim 23, wherein said pressure barriercomprises a polymeric film.
 25. The spoolable tube of claim 24, whereinsaid polymeric film is helically wrapped around said composite layer.26. The spoolabe tube of claim 24, wherein said pressure barriercomprises at least one of: polyethylene, cross-linked polyethylene,polyamide, polypropylene, polyvinylidene fluoride, and a polyester. 27.The spoolable tube of claim 1, further comprising an energy conductor.28. The spoolable tube of claim 1, wherein said composite layer furtherincludes a matrix.
 29. The spoolable tube of claim 28, wherein saidmatrix includes at least one of: a glue, a resin, and a polymer.
 30. Aspoolable tube comprising: an inner liner; an energy conductor; acomposite layer comprising high strength fibers; and an outer protectivelayer.
 31. The spoolable tube of claim 30, wherein said spoolable tubehas an open bore configuration when spooled on a reel.
 32. The spoolabletube of claim 30, wherein said composite layer comprises a resin. 33.The spoolable tube of claim 30, wherein said composite layer comprises aglue.
 34. The spoolable tube of claim 30, wherein said fibers compriseone or more of: glass, carbon and aramid.
 35. The spoolable tube ofclaim 30, wherein said fibers comprise glass.
 36. The spoolable tube ofclaim 30, wherein said fibers are helically wound about said innerliner.
 37. The spoolable tube of claim 30, wherein said energy conductorcomprises an optical medium.
 38. The spoolable tube of claim 37, whereinsaid energy conductor comprises an optical fiber.
 39. The spoolable tubeof claim 30, wherein said energy conductor comprises an electricallyconductive medium.
 40. The spoolable tube of claim 39, wherein saidenergy conductor comprises copper wire.
 41. The spoolabe tube of claim30, wherein said energy conductor is helically oriented.
 42. Thespoolable tube of claim 30, wherein said energy conductor is axiallyoriented.
 43. The spoolable tube of claim 30, wherein said energyconductor is embedded in said inner liner.
 44. The spoolable tube ofclaim 30, wherein said energy conductor is embedded in said compositelayer.
 45. The spoolable tube of claim 30, wherein said energy conductoris disposed between said inner liner and said composite layer.
 46. Thespoolabe tube of claim 30, wherein said energy conductor is disposedbetween said inner liner and said outer protective layer.
 47. Thespoolable tube of claim 45, wherein said energy conductor comprises anoptical medium or a electrically conductive medium.
 48. The spoolabletube of claim 47, further including a pressure barrier layer.
 49. Thespoolable tube of claim 48, wherein said pressure barrier comprises apolymeric film.
 50. The spoolable tube of claim 30, wherein said outerprotective layer further includes a coupling device.
 51. A spoolabletube comprising: inner layers comprising a liner and high strengthfibers helically wound about said liner; and a seamless outer protectivelayer holding said inner layers together; wherein said spoolable tubehas an open bore configuration when spooled on reel.
 52. The spoolabletube of claim 51, wherein said outer protective layer is seamless. 53.The spoolable tube of claim 51, wherein said inner layers furtherinclude a matrix.
 54. The spoolable tube of claim 51, wherein saidfibers have a distinct interface between said fibers.
 55. The spoolabletube of claim 53, wherein said matrix comprises a resin.
 56. Thespoolable tube of claim 53, wherein said matrix comprises a glue. 57.The spoolable tube of claim 53, wherein said matrix comprises a polymer.58. The spoolabe tube of claim 51, wherein said liner comprises athermoplastic.
 59. The spoolabe tube of claim 51, wherein said liner hasa melt temperature of at least 250° F.
 60. The spoolable tube of claim51, wherein said liner has an axial modulus of elasticity less than500,000 psi.
 61. The spoolable tube of claim 58, wherein said linercomprises at least one of: polyethylene, cross-linked polyethylene,polyamide, polypropylene, polyvinylidene fluoride, and a polyester. 62.The spoolable tube of claim 51, wherein said outer protective layerfurther includes a coupling device.
 63. The spoolable tube of claim 51,further including a coupling device.
 64. The spoolable tube of claim 51,wherein said fibers comprise one or more of: glass, carbon and aramid.65. The spoolable tube of claim 64, wherein said fibers comprise glass.66. The spoolable tube of claim 53, wherein said fibers comprise glass.67. The spoolable tube of claim 51, wherein said fibers are helicallywound about said inner liner at about ±30° to ±70° relative to thelongitudinal axis of said tube.
 68. The spoolable tube of claim 51,wherein said fibers include clockwise and counter-clockwise helicallyoriented fibers.
 69. The spoolable tube of claim 66, wherein said fibersinclude clockwise and counter-clockwise helically oriented fibers. 70.The spoolable tube of claim 51, wherein said outer protective layercomprises a polymer.
 71. The spoolable tube of claim 70, wherein saidouter protective layer comprises fillers.
 72. The spoolable tube ofclaim 51, further including a pressure barrier layer.
 73. The spoolabletube of claim 72, wherein said pressure barrier comprises a polymericfilm.
 74. The spoolable tube of claim 73, wherein said polymeric film ishelically wrapped around said composite layer.
 75. The spoolabe tube ofclaim 73, wherein said pressure barrier comprises at least one of:polyethylene, cross-linked polyethylene, polyamide, polypropylene,polyvinylidene fluoride, and a polyester.
 76. The spoolable tube ofclaim 73, further comprising an energy conductor.
 77. A tube comprising:an inner liner comprising a polymer; a first layer comprising glassfibers helically wound about the inner liner; an outer layer comprisingglass fibers helically wound about the first layer; and an outerprotective layer forming an outer surface, wherein the tube comprises atleast one layer of glass fibers wrapped in a helical direction and atleast one layer of glass fibers wrapped in second helical direction.